to get the full benifits of quad core in gamming you would need to spend illustrious amounts of money on other components too.
i have
pentium d dual core 3.4ghz
4gb ram
2 x200gb hdd
sapphire radion x1600 pro
and that is plentiful and can run anything i can throw at it up to now.,
your lag will mainly come with your internet connection and not so much the computer you are running it with.